In our 2001 GMC school bus there is a light that comes on for range inhibited condition. Here is what my Allison manual says. Range inhibited light will come on if...."The purpose of the range inhibited light is to alert the driver that transmission operation is being inhibited and that range shifts being requested by the operator may not occur. When certain operating conditions are detected by the TCM the control will command the transmission to be locked in that range if in use. If the torque converter clutch is applied when condition is detected the clutch will disengage concurrently with the activation of range inhibited light. Causes for shift inibit lights.
Above idle neutral to range shifts
Forward/reverse directional shifts
transmission problems(obviously)
Auxillary equipment operation (PTO)?
Pretty much goes on to state It shows a potential problem inn the transmission and to get you butt to a dealership to check it out. Goes onto state it can also show a problem between engine and transmission. Hope this may help. Maybe your just shifting your truck a little to quick from park to gear... Or maybe your not giving the transmission enough time after it is put into drive? Hope I helped a little. Bill

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2002 Dmax, A few 6.5\'s, And a 6.2 <br />Gmanjr96@aol.com

My new 2003 did this with just 73 miles on it. In my case this message appeared when the truck was shifted into reverse but, it would not engage the gear. This condition did not resolve it self and I returned it the dealership. I was informed that the truck posted no codes and that the problem was very hard to determine. I informed them that they would send a tech to ride each and every day with my wife to work, so that he could push the truck backwards when this no problem occurred. Later that day it was determined that the truck had a bad solanoid in the trany. No problems since. I posted to tell you this because these clowns at the dealership burned up over a half tank of my fuel performing this repair. I did get them to fill the truck up as well. I am sure they were glad to see me leave. Good Luck.

Thanks for the responses. No there was no high idle when I shifted. Just shifted as normal. Both times were the first shift after it was started. It sounds like some problem that I had better get into the dealer to document.